Water control system for suction rolls in papermaking machines

ABSTRACT

A water control system for suction rolls generally and couch rolls particularly for a papermaking process of the type wherein water is removed from the wet paper web that has been run around the roll. The improvement comprises forming a surface tension covering around the periphery of the couch roll on at least a portion of the couch roll and providing a water control zone within the couch roll to control the water removed from the paper to the surface tension member and finally varying the pressure within the water control zone so as to be able to directionally control the discharge of water off the couch roll in a predetermined pattern for deposit in the water collecting pan provided in proximity to the couch roll. The water control zone may comprise a three-zone system comprising a water collecting zone, a transfer zone and a release zone with a relatively small vacuum being utilized in the transfer zone in comparison to the magnitude of the vacuum being utilized in the water collecting zone so that the surface tension covering and the vacuum differential coact to cause the water to be held at the surface of the couch roll just prior to the release zone so that it can be released in a controlled pattern. Additionally the water control zone can include a fourth zone which can either be a void zone at atmospheric pressure or a final zone having a vacuum induced therein to assist the surface tension covering in maintaining any residual water at the surface of the couch roll. Also disclosed is a method for improving the removal of water from a traveling paper web by subjecting the web to various induced vacuums from within a rotating couch roll in the papermaking process. The surface tension covering can be for example a wire screen which has a film-forming action with the water and produces a film-like collection of water in its interstices.

United States Patent [191 Zentner et al.

[451 Sept. 2, 1975 WATER CONTROL SYSTEM FOR SUCTION ROLLS IN PAPERMAKING MACHINES [75] Inventors: Thomas G. Zentner; Raymond L. Dawson; Grady E. Lee, Jr., all of Monroe, La.

[73] Assignee: Olinkraft, Inc., West Monroe, La.

[22] Filed: June 28, 1974 21 Appl. No.: 483,649

Related US. Application Data [63] Continuation-in-part of Ser. No. 285,108, Aug. 30,

1972, abandoned.

[52] US. Cl 162/199: 29/121 R; 162/217; 162/274; 162/369; 162/370', 162/372;

[51] Int. Cl D2lf 3/10; D2lf 7/00 [58] Field of Search 162/199, 306, 217, 274,

162/365, 369, 370, 372, DIG. 7, 307; I

Primary Examiner-S. Leon Bashore Assistant ExaminerRic hard H. Tushin Attorney, Agent, or Firm-C. Emmett Pugh; Calvin J.

Laiche; Norvell Von Behren [57] ABSTRACT A water control system for suction rolls generally and trol zone within the couch roll to control the water removed from the paper to the surface tension member and finally varying the pressure within the water control zone so as to be able to directionally control the discharge of water off the couch roll in a predetermined pattern for deposit in the water collecting pan provided in1 proximity to the couch roll. The water control zone may comprise a three-zone system comprising a water collecting zone, a transfer zone and a release zone with a relatively small vacuum being utilized in the transfer zone in comparison to the magnitude of the vacuum being utilized in the water collecting zone so th'atfthe surface tension covering and the vacuum differential coact to cause the water to be held at the surface of the couch roll just prior to the release zone so that it can be released in a controlled pattern. Additionally the water control zone can include a fourth zone which can either be a void zone at atmospheric pressure or a final zone having a vacuum induced therein to assist the surface tension covering in maintaining any residual water at the surface of the couch roll. Also disclosed is a method for improving the removal of water from a traveling paper web by subjecting the web to various induced vacuums from within a rotating couch roll in the papermaking process. The surface tension covering can be for example a wire screen which has a film-forming action with the water and produces a film-like collection of water in its interstices. 1

38 Claims, 11 Drawing Figures PATEHTEU 25975 3,902,960

SiiKU 1 OF 5 FIG. I PRIOR ART PRIOR ART PATENTED SEP 2 I975 sum 3 OF 5 FIG.6

HIGH VACUUM LOW VACUUM ATMOSPHERE ATMOSPHERE OR VACUUM WATER COLLECTING ZONE TRANSFER ZONE RELEASE ZONE FINAL OR VOID ZONE FIG.

.i";"TTEHTE[ISEP 2l975 3,902,966

saw u UF 5 THE EFFECT OF WIRE MESH AND DISCHARGE RATE ON OBTAINING A GOOD DISCHARGE PATTERN 25 e000 DISCHARGE PATTERN AREA 20 BAD DISCHARGE PATTERN MINIMUM GPM ALLOWING A GOOD OBTAINED IN THIS AREA DISCHARGE PATTERN O 500 I 000 I500 2000 2500 HOLES PER SQUARE INCH BASED ON WIRE MESH FIG. 9

PATH-HED 2|975 3 902 960 GOOD DISCHARGE PATTERN AS RELATED TO THE FOURTH VACUUM ZONE AND THE DISCHARGE RATE ,DRY WIRE 6 SURFACE. 35

(INCHES H A soon DISCHARGE PATTERN IS BAD DI A OBTAINED IN THIS\( 5 PATTERN AREA 1 AREA 3 O 5 IO I5 WATER FLOW METERED TO THE FELT (6PM) FIG. IO

WATER CONTROL SYSTEM FOR SUCTION ROLLS IN PAPERMAKING MACHINES REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of the prior copending application Ser. No. 285,108 entitled Improved Suction Roll and Method of Water Removal filed Aug. 30, 1972, now abandoned, the earlier parent application disclosing the present invention in its more general terms with the present application adding in further detailed disclosures particularly but not exclusively with respect to the preferred mesh size ranges for the surface tension covering and the vacuum levels in the fourth, final zone of the most preferred embodiments of the present invention, which detailed disclosures were developed as a result of experimental work, some of which continued on after the filing of the parent application.

BACKGROUND OF THE INVENTION This invention relates generally to the papermaking process and more particularly to a new and novel suction roll and suction roll water removalsystem and method used in the paper-making process for removing water at for example the couch roll of the process. Because the present invention has particular but not exclusive application to couch rolls, the present invention will be primarily discussed and disclosed with respect to the couch roll art. 1

In the earlier development of the art of papermaking, the forerunner of the modern papermaking machine was known as the Fourdrinier machine which was a generally horizontal papermaking machine having a headbox which delivered the liquid paper pulp stock onto traveling screen through a slice in the headbox. The traveling screens or wire were generally supported first by a breast roll and then by various primary and secondary forming boards which were the prime removers of water from the paper stock. After passing over suction boxes, the wire and the paper stock then passed over a couch roll which served to drive the wires in the Fourdrinier machine and also to remove more moisture from the paper stock prior to its being sent to the web pressing and drying portion of the papermaking process. For a comprehensive review of the Fourdrinier machine reference should be made to Volume III of the three-volume work entitled Pulp and Paper Manufacture" prepared under the direction of the Joint Textbook Committee of the paper industry and edited by Ronald G. MacDonald and published by McGraw-Hill Book Company, copyright 1970 and bearing the Library of Congress catalog card No. 68-20994. The Fourdrinier papermaking machine is described in Chapter 6 of that volume starting on Page 245 and running through Page 295 with a detailed description of the couch roll being given on Page 286 and 287 of the same volume. As can be seen in FIG. 6-43 of that Volume on Page 287 the couch roll of a Fourdrinier machine generally comprises an outer shell which has a plurality of radial holes drilled therein with the holes being in contact with the inner portion of the couch roll which may be sectionalized to various vacuum or pressure sources.

PRIOR ART PAPRIFORMER (FIG. 1)

As the technology in papermaking advanced, various types of papermaking machines evolved which have been generally classified in cylinder-type machines and these are detailed in Chapter 7 of the same reference volume starting on Page 297 and running through Page 365. The cylinder-type papermaking machines are of many varieties. However, all are equipped with a couch roll at the end of the process which functions, in addition to other functions, to remove more water from the paper stock prior to its being transferred to the next stage in the papermaking process. By referring to FIG. 1 of the drawing of this invention and also by referring to the referenced volume on Page 337 at FIG. 7-32 there is shown one of the cylinder-type of papermaking machines known in the trade as the Papriformer and comprises basically a plurality of rolls described as the breast roll 10, the forming roll 12 and the couch roll 14 around which a top screen 16 and a bottom screen 18 are transported-with a plurality of water collecting pans 20 and 22 being formed in proximity to these rolls for the purpose of collecting the water extracted from the paper web which is formed between the traveling screens 16 and 18.

For a more detailed description of the Papriformer, reference should be made to an article entitled The Papriformer Part I The Machine and Its Performance authored by R. de Montigny, I. T. Pye and T. b. Hedley as published in the Pulp and Paper Magazine of Canada; 68, No. 10; T-482-T-505 (October, 1967). The forming roll 12 in the Papriformer described comprises a generally two-zone vacuum section while the couch roll 14 comprises a generally fourzone section with a positive pressure being induced in the first zone 24 with an intermediate zone 26 of atmospheric pressure being followed by two zones of vacuum 28 and 30 as more detailed in the last cited reference article. It is known in the art to provide the forming rolls 12 of the Papriformer and also the forming rolls of the other methods of papermaking with wire coverings which are used in conjunction with multizone vacuum zones 32 and 34 for the purpose of extracting water from the traveling paper web with the vacuums in the multi-zones 32 and 34 generally being low in the range of ten inches of water in order to draw large amounts of water into the forming roll for subsequent removal. To applicants knowledge it is not known in the art to apply a wire or surface tension covering to the couch roll or any other type of suction roll in combination with the new and novel water control zone which is formed within the roll and which will be described more fully hereinafter.

PRIOR ART VERTI-FORMA (FIGS. 2 and 3) Referring now to FIGS. 2 and 3 of the drawings, there is shown another variation of the conventional type papermaking machine known in the trade as the Verti- Forma and which comprises a pair of breast rolls 36 and 38 in combination with a couch roll 40 and a drive roll 42 with a pair of traveling wires 44 and 46 being utilized to contain the pulp stock 48 supplied by the headbox 50. A drive roll 52 carries the semi-formed paper, that is the wet paper web, 54 to the next stage in the paper forming process as is well known in the art. For a more detailed description of the Verti-Forma, reference should be made to the article entitled Through A Glass, Darkly (A Discussion of New Sheet Formers) by R. de Montigny in the Pulp and Paper Magazine of Canada, October 1966 issue.

When used in the Verti-Forma, the couch roll 40 functions as a means to remove more water from the paper 54 as it passes around a portion of the periphery of the couch roll and attempts to discharge the water into a collector pan 56 formed in proximity to the couch roll. As supplied from the manufacturer. the couch roll 40 has formed therein a low vacuum zone 58 and a high vacuum zone 60 with the remaining portion of the couch roll interior being a void zone 62 or a zone in which neither pressure nor vacuum was formed. The manufacturers supplied couch roll also contained provision which allowed the low vacuum zone 58 and the high vacuum zone 60 to be rotated in the direction shown by the arrow 64 within the void zone 62 in order that some control could be achieved over the discharge of the water from the periphery of the couch roll. The problem encountered with this couch roll design was that, while the collector pan 56 collected some of the water thrown from the couch roll after the wire 46 left the couch roll surface, a greater portion of the water would rim around the periphery of the couch roll as shown by the arrows 66 and would not be collected by the collector pan 56 but would be redeposited in an uneven pattern back on the wet upper web 54 coming into contact initially with the couch roll 40. As a result of this condition, the couch roll 40 was unable to remove sufficient water from the paper web 54 causing the paper web 54 to contain excess water which later caused excessive downtime in the production of the paper during a later stage of the papermaking process. The down times were caused by breaks in the paper web at the first press rolls downstream from the couch roll which resulted from the excess water being contained in the paper web. Before solving the problem with the subject invention, the number of breaks at the press rolls was running in the range of twenty per day requiring approximately to 45 minutes apiece downtime before the problem could be corrected and the papermaking process started up again.

Initial attempts at using factory-designed couch roll 40 began by inducing low vacuums in the low vacuum zone 58 ranging in the vicinity of fifteen inches of mercury with high vacuums in the high vacuum zone 60 ranging in the vicinity of inches of mercury. In addition the two vacuum zones were rotated in the direction shown by the arrow 64 in the hope that a different position of the vacuum zones would cure the problem, but this did not solve the problem and the water continlied to rim the couch roll in the direction shown by the arrows 66 and thrown back into the paper web 54. Other attempts were made to solve the problem such as applying more vacuum to the vacuum zones 58 and 60 in order to try to pull the water up through the couch roll openings into the vacuum system and also attempts were made to re-design the collector pan 56 and also to provide additional collector pans around the couch roll, however, these efforts failed also. Attempts were also made at preventing the water from being thrown back onto the traveling web 54 by the installation of water doctoring devices such as knives which would scrape the couch roll and remove the water therefrom and also attempts were made at completely disconnecting the vacuum from the couch roll so that it acted only as a turning roll at the end of the run with no water removal being attempted at that point. While this last attempt somewhat eliminated the problem of throwing of water back onto the paper web,

it did not at :lve the problem of excess water in the paper web sincc. the couch roll was not removing any water and the la er failure of the paper web at the first press rolls continued to exist with loss in production on the machine.

SUMMARY OF THE INVENTION In order to overcome the problems inherent in the design of the prior art papermaking machines both of the Fourdrinier type and the cylinder type, there has been provided in the preferred embodiment of the present invention a new and novel couch roll and couch roll water removal system which may be used in conjunction with the method disclosed by the subject invention to precisely control the amount of water removed from the traveling paper web at the couch roll so that the amount of water in the paper web may be also precisely controlled. This is accomplished by form ing a surface tension covering around at least a portion of the periphery of the couch roll and by precisely controlling the vacuum in the water control zone formed within the couch roll so that the surface tension covering and the vacuum control coact to cause the water to be held at the surface of the couch roll just prior to being released into the collector pan. The surface tension covering around the couch roll may take the form of a wire mesh screen either metallic or non-metallic, fixedly attached to the outer surface of the couch roll or may take other forms as will be described more fully hereinafter. The water control zone formed within the couch roll may take the form of a single zone or a multi-zone such as the three-zone system (water collection, transfer and release zones) or four-zone system (the latter including a final vacuum zone) shown in the preferred embodiments and may also encompass other sub-zones or sections within the spirit and scope of the invention. With the use of the surface tension covering on the couch roll in combination with the precisely controlled vacuum in the water control zone within the couch roll, a uniformly controlled pattern of water may be thrown from the couch roll into the collector pan with the result that the rimming of water on the couch roll back in to the paper web is minimized, if not completely eliminated, depending upon the variation in the controlled vacuum in the water transfer zone and the final zone and also depending upon the amount of water and the manner in which it is held in the surface tension covering.

It should be further appreciated that the present invention, including the surface tension covering and the water control zone, can be applied to suction rolls other than the couch roll, although it has particularly efficacious application to the latter.

Accordingly it is an object of the preferred embodiment of the invention to provide a new and improved water removal system for a papermaking process wherein the water is removed from the paper that has been run around the couch roll of the papermaking process so that the water can be thrown from the couch roll in a controlled directional pattern into a collector means without being thrown back on the paper web incoming to the couch roll.

Another more general object of the invention is to provide an improved suction roll, couch roll or otherwise, which has formed thereon a surface tension covering around at least a portion of the periphery thereof with the surface tension covering acting in combination with a precisely controlled vacuum from within the suction roll to achieve the desired water control effects.

Still another object of the invention is to provide an improved suction roll, couch roll or otherwise, having a water control zone comprising a transfer section and a water collection section wherein a relatively small vacuum is utilized in the transfer section in comparison to the magnitude of vacuum in the water collection section.

Yet another object of the invention is to provide a new and novel suction roll, couch roll or otherwise having a water control zone comprising at least a transfer zone which is formed therein and which initiates at a point approximately where the paper web leaves the roll with the transfer zone terminating approximately at the collector pan so that the surface tension covering formed on the surface of the roll can coact with the precisely controlled vacuum formed within the transfer section to directionally control the thrown of water form the roll into the collector pan.

Still yet another object of the preferred embodiment of the invention is to provide a new and novel suction roll, couch roll or otherwise, having a surface tension covering formed thereon in combination with at least a three-zone water control system with the first zone being a water collection zone having a relatively high vacuum induced therein, the second zone being a transfer or transition zone having a relatively low vacuum induced therein in comparison to the vacuum in the water collection zone, and the third zone being a release zone having a variable pressure ranged sufficiently to allow the centrifugal force caused by the retation of the couch roll to pull the water from the surface tension member into the collector pan in a precisely controlled directional pattern.

Yet another object of the invention is to provide a new and novel method for improving the removal of water in a papermaking process at a suction roll, such as for example a couch roll, in order to remove the water to a collector pan position in proximity to the suction roll and to prevent rimming of the water on the suction roll back into the incoming paper web at the suction roll surface.

Still another object of the invention is to provide a new and improved suction roll for a papermaking process wherein the suction roll is covered with a surface tension member which acts as a film-forming barrier to prevent discharge of residual water in the fourth, void zone of the suction roll.

These objects and other advantages of the present invention will become apparent from a reading of the detailed description of the preferred embodiments of the invention presented below and from a review of the drawings of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing the cylindrical type paperformer known in the prior art as the Papriformer";

FIG. 2 is a schematic diagram of the paperformer known in the prior art as the Verti-Forma;

FIG. 3 is an enlarged cross-sectional view of the couch roll 40 area of the Verti-Forma shown in FIG. 2;

FIGS. 4A and 4B are cross-sectional views of the same couch roll area as shown in FIG. 3 but also showing the modifications that have been made to the couch roll in order to achieve the desired results of the preferred embodiment of the present invention, 4A and 48 being substantially identical except that detailed references numerals are used in the interior of the couch roll while legends are used in the latter;

FIG. 5 is an enalrged cross-sectional view taken along section lines 55 of FIGS. 4A and 48 showing the surface tension covering applied to the couch roll shell with the water retained in the surface tension covering;

FIG. 6 is a cross-sectional view similar to FIG. 5 showing the surface tension covering comprising a plurality of wire screens; and

FIG. 7 is a perspective view showing the shell of a couch roll with the surface tension covering being formed around the periphery thereof and also showing a portion of the surface tension covering removed to shown the existing radial holes in the couch roll;

FIG. 8 is a schematic view showing the relative vacuum/pressure sources used for the four zones in the most preferred embodiment of the present invention, with the last, void zone being shown also with an alternative embodiment;

FIGS. 9 and 10 are graphical illustrations summarizing certain test data done on a particular pilot plant suction roll modified to simulate a couch roll.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings in general and in particular to FIGS. 4-8 of the drawings, there are shown as the preferred embodiments of the present invention the modifications that have been made to a couch roll, as the preferred and most efficacious application of the present invention, whereby the unusual results described herein have been obtained. However, it should be understood that the present invention may likewise be applied to other types of suction rolls.

SURFACE TENSION COVERING When experimenting with the laboratory test model of a papermaking facility, it was found that one necessary element needed to control the discharge pattern of water from the couch roll is to provide the couch roll or at least a portion of the couch roll with a surface covering capable of acting as a surface tension member. The surface tension covering provided should contain holes, grids or other openings to allow water to move into and out of the existing holes 68 drilled in the couch roll shell 70 as shown in the drawings. However, the holes, grids or other openings should be of a size that would allow a film-forming action to take place between it and the water in the manner to be described more fully hereinafter and may be formed for example of available metallic or non-metallic wire screens having a varying wire mesh which are readily available to the paper industry. Although the mechanism of the sur-v face tension covering may not be fully understood, it is believed to act as a restraining partition and a surface on which the water rides as it passes through the transfer zone 86 and final/void zone 96, as described more fully hereinafter. This film-forming action is similar to what one might observe when a static window screen is sprayed with water some water is trapped in the openings of the screen by a surface tension phe nomenon.

These couch roll coverings, shown generally by the numeral 72 in FIGS. 57, could comprise a single layer of mesh formed generally by a plurality of wires 74 interwoven with a plurality of other wires 76 to produce a wire mesh screen of the type similar in structural appearance to that used in a household screen door. On the other hand, as a variation on the surface tension covering, the screen 72 may be formed, as shown in FIG. 6 of the drawings, by fixedly attaching a top screen 78 to a bottom screen 80 with the screens being fixedly attached either to each other or to the surface 82 of the couch roll shell 70.

Other variations of the surface tension covering may be utilized without departing from the spirit and scope of the invention. For example the surface tension cov ering may be formed by utilizing lands and grooves machined on an existing couch roll or may be formed by etching the couch roll and may also be formed by fixedly attaching a wire or wires over at least the existing opening 68 in the couch roll leaving the remaining portion of the couch roll uncovered. Still other variations in the surface tension member may comprise providing spirals or grooves in the couch roll shell with a surface tension member being formed at least over the spirals or grooves.

As beforementioned the broad concept of wire covering a forming roll or other rolls in papermaking machines appears to be known in the paper industry. However, it is believed that the concept of wire covering a suction roll and in particular the couch roll for the express purpose of aiding in the controlled directional patterned release of the water from the couch roll is new to the papermaking process and novel. When wire coverings had been applied on forming rolls or other rolls in the prior art, it was generally used in a condition in which the water was removed from the paper through the internal vacuum system of the forming roll. In the two instances known to date where the wire covered forming roll is used to discharge water externally (in the Papriformer hereinbefore described and in the process known as the Multi-former") the wire covered roll acts solely as a forming roll wherein the fiber-water slurry is drained on the wire covering at a consistency of 0.2 to 1.5 per cent to form a wet web with a consistency generally in the to 12 per cent range and the wire does not constitute a surface tension member forming a film-like collection of water. In distinction the couch roll used in the papermaking process is a wet web water removing device which generally utilizes higher vacuums and takes the consistency of the already formed web from the to 16 per cent range to above the 18 per cent solid range and the wire does serve as a surface tension member.

WATER CONTROL ZONE GENERALLY As beforementioned in addition to the use of a surface tension covering around at least a portion of the periphery of the couch roll, the new and novel suction roll and water removal system of the invention comprises a unique water control zone which will now be described in more detail. In the preferred embodiment shown by this disclosure, it has been found that the preferred internal arrangement of the couch roll should provide for at least three or four sub-zones or sections which are separately controllable for the purpose of being able to directionally control the discharge of water from the couch roll. In describing the water control zone and its elemental parts, it should be understood that zone, sub-zone and section are usually used interchangeably.

WATER COLLECTION ZONE The first of the water control zones can generally be referred to as a water collection zone 84 which should be a relatively high vacuum zone ranging from approximately 5 inches of mercury to approximately 12 or more inches of mercury. Indeed, for example, a vacuum level of 15 or 20 inches of mercury could be used. The water collection zone may preferably encompass as much of the area of the couch in direct contact with the drainage wires 46 and the wet paper web 54 as possible, however a lesser portion of this same area may perhaps be satisfactory, recognizing the fact that this would result in less time for de-watering of the wet paper web 54 by the couch roll.

It is conceivable that many vacuum ranges could be utilized in the water collection zone 84, and for the purposes of this application the high vacuum induced in the water collection zone can probably be defined as any vacuum greater than approximately 2 inches of mercury which is equivalent to approximately 25 inches of water. While an experimental pilot plant operation utilized high vacuums of 2 to 7 inches of mercury, it is conceivable that a production unit should work mainly between the vacuum range of approximately 5 and approximately 12 inches of mercury or more in the water collection zone 84. It should be noted that the higher the vacuum in the water collection zone 84, the greater the capacity of the radial holes 68 in the couch in combination with the surface tension member to remove the water for later discharge as will be more fully described hereinafter. Accordingly it is foreseeable that high vacuums of up to approximately 28 inches of mercury might be desirable in some instances in the papermaking process.

In the operation of most couches in the papermaking process, it is desirable to pull some air through the paper web to assure maximum web dryness and this could be done in the high vacuum water collection zone if possible. It should also be noted that this accompaniment of air with the water removal in the water collection zone further distinguishes the operation of the most preferred couch roll embodiment from that of a forming roll which does not pull air on the vacuum forming roll but only pulls water through the couch roll.

TRANSFER ZONE Immediately following the water collection zone in the preferred embodiment is a transfer or transition zone 86 which has formed therein a relatively small vacuum in comparison to the magnitude of the vacuum being formed in the water collection zone. From experimentation it has been found that, whenever the vacuum in the water collection zone 84 ranges from approximately 5 to approximately 12 inches of mercury, then the preferred vacuum in the transfer zone 86 would range from approximately 0 inches of water to approximately 10 inches of water.

The transfer zone 86 acts as a transition zone to prevent the early discharge of water from the couch roll as the wire 46 is separated from the couch roll at the point 88 as shown in FIGS. 4A and B of the drawings. Therefore it is preferable that the transfer zone 86 initiate approximately in the area of the paper stock leaving the couch roll as shown by the numeral 88 in the drawing and terminate somewhere in the vicinity of the beginning of the collector means as shown by the numeral 90 in the same figure. It is possible to locate the start of the transfer zone 86 at a point prior to the point of departure of the wire 46 from the couch roll, however, it is probably not desirable to locate it after the point of the wire and paper separation since this would allow extraneous air to be drawn from the ends of the couch roll into the high vacuum water collection zone 84. The end of the transfer zone 90 should be located at a position such that the subsequent water release pattern clearly enters the water collector pan 56 without impinging on the lip 92 of the collector pan. It is inter alia within the transfer zone 86 that the surface tension covering applied to the couch roll exhibits its importance since it acts as a surface tension member on which the water in the couch roll holes 68, previously removed by the high vacuum zone, are re-deposited in the surface tension member in a film-like manner. The openings in the couch roll covering fill with water according to the size of the openings in the couch roll covering and the surface tension of the water. While normally the water in the surface tension member would tend to be discharged from the couch while passing through the transfer zone 86 as a result of the centrifugal force created by the rotation of the couch, with the low vacuum applied from within the transfer zone 86, this centrifugal force is overcome and the water remains on the surface tension member and possibly within the openings 68 in the couch shell 70 until it is released as the couch roll shell 70 passes through the third or release zone of the multi-zone system.

In experimental work performed on a test unit, vacuums in the transfer zone ranging from approximately zero to approximately 10 inches of water have given satisfactory results with the best results appearing to be between about 2 and about 5 inches of water for pilot plant conditions. It is foreseeable that higher vacuums may be expected at higher operating speeds of a paperforming machine, ranging from 1500 to 3000 feet per minute. and with higher volumes of water than possible on the pilot plant model.

RELEASE ZONE Immediately following the transfer zone 86 is the third zone of the preferred embodiment multi-zone system wherein there is formed a release zone 94 which, as the name implies, is the zone in which the water is released from the surface tension covering and from the couch hole openings 68. This zone 94 follows the low vacuum transfer zone 86 and appears to work satisfactory when vented to the atmosphere with a vent of sufficient size that air enters the release zone 94 naturally as designated by the amount of water discharged from the couch. Test experiments also indicate that the release zone 94 may also work at certain conditions of vacuum and pressure but these conditions do not appear critical in relationship to the air vented condition. In the release zone 94, the surface tension covering again becomes of significance to the operation of the zone in that it controls the water discharge pattern. As the vacuum on the film-like collection of water developed in the transfer zone 86 is broken as the couch shell 70 passes into this zone, the water is discharged from and through the surface tension covering rapidly because of the waters close proximity to the surface of the couch roll.

FINAL/VOID ZONE It is believed that a residual amount of water is carried in the couch roll openings 68 while the couch roll passes over the void zone 96 in an equilibrium state and the surface tension covering acts to retard further discharge of this equilibrium water by acting as a barrier and by retaining any water thus collected through new surface tension forces which are relatively large for the small droplets of water. It is thought that this action also tends to prevent the rimming of the water as beforementioned on the outer surface of the couch roll and into the incoming paper web.

It should also be pointed out that numerous variations of the physical vacuum zone arrangements are conceivable to obtain a desired and controllable water release pattern with possible improvements thereon. For example, some experiments have shown that the void zone 96 may function by being vented to the atmosphere, vented to the release zone 94 through the valved opening 98 or by removing the seal 112 in the wall 100.

In addition, the void zone 96 may be made into a fourth or final vacuum zone in which any vacuum may be used which-is sufficient to prevent discharge of the aforementioned residual water. A vacuum level range of approximately 2 to 4 inches of water should be generally adequate. This variation, in which the void zone 96 is made a fourth or final vacuum zone appears to offer an even more significant improvement in the operation of the couch in that a more concise water discharge pattern may be obtained with lesser requirements on the transfer vacuum zone control.

It is noted that, as illustrated in FIGS. 4A and 4B, the void or final zone 96 extends from the termination of the release zone 94 to the initiation of the water collection zone 84, the four zones spanning the full 360 degrees of the roll.

ZONES GENERALLY As beforementioned, the water control zone in the preferred embodiment may be formed as a three-zone system incorporating a water collection zone 84, a transfer zone 86 and a release zone 94, and may also be preferably formed as a four-zone system as beforementioned. It has been found from experimentation that by varying the relatively low vacuum in the transfer zone 86, the operator is able to precisely control the pattern of the water throw off from the couch roll into the collector pan 56. Whenever the low vacuum in the transfer zone 86 is in the low range the pattern can be precisely controlled to that shown by the arrow 102; and, when the low vacuum in the transfer zone is in the high range, the water pattern can be varied to that shown by the pattern shown in arrow 104 since it takes longer to release this higher vacuum as the shell of the couch passes into the release zone 94.

In the formation of the multi-zone water control zone of the invention, the water collection zone 84 is formed by means of a pair of walls 106 and 108, with the wall 108 also forming one wall of the transfer zone 86 with the second wall of the transfer zone 86 being formed by the wall 110, all in a manner well known in the art. The walls 100, 106, 108 and 110 all have formed at the exterior portion thereof a seal 112, as is well known in the art of couch roll design.

As shown schematically in FIGS. 4A and B and 8, the relatively high vacuum formed in the water collection zone 84 is induced by the vacuum opening 114 while the relatively low vacuum formed in the transfer zone 84 is induced through the vacuum opening 116 as is well known in the art. As beforementioned, the vent in the release zone 94 is induced by means of the opening 118, while the void zone 96 can be vented as aforedescribed or become a final vacuum zone induced through vacuum opening 119.

' When the water control zone is formed in other than a three or four zone system as taught by the most preferred embodiments, it is within the spirit and scope of the invention that the pressure in the water control zone could be varied by other means so as to be able to directionally control the flow of water off the couch roll in any pre-determined pattern for deposit in the water collecting pan. For example the water control zone could comprise at least two zones with the pressure in one zone being a variable vacuum sufficient to counteract the centrifugal effects of the rotation of the couch roll, while the pressure in the other zone is variable to release the water thereby allowing the centrifugal action of the couch roll on the water to pull the water from the surface tension member and into the collector means with the couch roll being covered with the beforedescribed surface tension covering.

When practicing the method of the invention, first the exterior surface of the couch roll is provided with a surface tension covering of the type or types beforementioned and thereafter the web is passed over the water control zone in the couch roll while inducing a pre-determined vacuum in the water control zone. The water control zone may be a one, two, three, four or other multi-zone system within the spirit and scope of the invention, and after the web is passed over the water collection zone the vacuum in the water control zone will be reduced to a much lesser vacuum sufficient to hold the water in the surface tension covering against the centrifugal effects caused by the rotation of the couch roll. Thereafter the pressure in the water control zone is reduced to a pressure sufficient to allow the water held in the surface tension cover to be released in a controllable pattern as a result of the centrifugal force caused by the rotational effect of the couch roll to thereby allow the water to be collected in the collector pan. Any residual water may be retained in the couch roll openings by the surface tension member as the couch shell passes over the void or final zone.

From the above it becomes apparent that there has been provided by the subject disclosure a new and unique suction roll and suction roll water removal system for the papermaking process, having particular application to couch rolls, wherein water is removed from the wet web and is subsequently discharged in a controllable manner which is non-distributive to the rest of the papermaking process. The water is removed from the wet paper web in a high vacuum zone ranging from approximately 2 to approximately 28 inches of mercury passing through a surface tension covering formed on at least a portion of the couch roll and is entrapped partially in the holes in the couch roll and in the surface area of the surface tension covering. In the transfer zone a momentary state of equilibrium is obtained in which the vacuum and the surface tension forces counteract the centrifugal forces developed by the rotation of the couch roll to maintain the water in the surface tension covering and near the surface of the couch roll within the couch roll openings. This is followed by a rapid discharge of the water into the collector pan in a manner and pattern which is determined by the location of the release or discharge zone and the surface tension member in relationship to the collector pan. Any residual water remains in the couch roll openings by being retained there by the surface tension covering, as the couch roll shell passes over the void area or, alternatively over the fourth, final, vacuum zone.

Additional Test Data There are of course many variable factors to be considered in designing a specific couch roll or other suction roll using the present invention. Among them are the basic specifics of the roll and paper themselves, viz., the speed of rotation of the roll in operation, the diameter of the roll, the relative angular positions of the roll and wet paper web, the type and content of the paper web, the amount of water being handled, and size and position of the water collector means (saveall pan). The specifics of these environmental factors will then determine the optimum flow-through characteristics of the surface tension covering (e.g. mesh size), and the optimal relative pressure/vacuum levels in the various sub-zones. Variation in any one of these factors can cause variation in one or more of the others, and usually some testing for each specific combination will be necessary to obtain optimum results. Thus, in each application, there must generally be a proper balancing or use of centrifugal force, surface tension and relative pressures and vacuums; with the centrifugal force being dependent upon the amount of water present and speed dictated by the paper machine operator, and the centrifugal force being balanced, when it is desired to do so, by the characteristics of the surface tension member and the relative pressures and vacuums of the water control sub-zones. Thus in the transfer zone 86 the centrifugal force is precisely offset by the film-forming action of the surface tension covering and the amount of vacuum so that the water is held near the surface of the roll so that the discharge can be rapid and controlled.

(It is noted that this near-surface holding of the water is illustrated schematically in FIGS. 5 and 6 which show the water film formed by the wire screen members 72 and 78, 80, respectively, near and at the surface 82 of the couch roll shell 70.)

If there were no surface tension covering to induce the formation of a water film, then air would enter the system and the water would be present in a noncontinuous form. Of course high vacuum levels might be used to retain the discontinuous water in the roll shell by movement of air into the shell. However, on release of the vacuum, the water would not be at the surface for immediate release and therefore would be discharged 'over too long a period of time.

Likewise, in the most preferred embodiment wherein a small vacuum is used for the final zone 96, any residual water is retained by the surface tension member through surface tension, film-forming effects which can become relatively immense for very small water droplets. This action, as mentioned above, prevents further undesired discharges of water past the release zone, eliminating the problem of rewetting the incoming paper web.

With all the guidelines discussed and specific teachings herein contained, one skilled in this art would be SPECIFICS PILOT MANCHESTER MULTLFORMER COUCH (N (No.

Width l8" I80" Diameter 38" 30%" Maximum Speed 1400+ fpm 2200 fpm Water Collection lntcrnal Boxes l Forming Zone Zone 2) Holding Zone 3) Transfer Zone Transfer Zone Release Zone 4) Void Zone Void Zone Water Removal From the headbox and Thru a wire and through wet, continwet web uous felt simulating water removal from a wet web Discharge Angle About l() over the Above 45 over the horizontal horizontal In the extensive tests run on the converted, pilot plant Multi-Former roll, where appropriate, felt was placed over the area of the roll corresponding to the water collection zone to simulate the paper web which would exist there in an actual Verti-forma couch.

As to mesh sizes for the surface tension covering, based on some initial tests done on the pilot plant, converted Multi-Former, it was concluded that a single l l4 mesh wire screen covering alone for the couch was too large to aid significantly in the control of water removal from the suction couch roll, while a single 60 40 mesh wire screen worked satisfactorily, and the combination of a 60 40 screen over a x14 backing wire gave good results.

An additional preliminary test run with a l6 l6 aluminum mesh wire screen (obtained from a local hardware store and of the type normally used for home window screen) indicated that it was possible to obtain satisfactory control over the water discharge pattern from the couch roll. However the results were not as good as for the 60 40 mesh, that is the release of the water from the roll appeared to be slightly sooner than for the 6OX4O mesh wire and possibly ending slightly later with the result of an apparently wider discharge pattern; although the initial point of release on the l6 l6 mesh wire appeared to be within the transfer zone. However, the test was run at an equivalent water discharge rate of 30 GPM which is generally a higher level than that which occurs in a couch roll.

Further testing of various mesh sizes on pilot machine No. 1 led to the conclusion that, as compared to 60x40 or 56x36 mesh bronze wires, a more open 40 mesh stainless steel wire does not give as good a discharge pattern nor is control thereof by manipulating the various vacuum levels as good as for the finer mesh bronze wires. It should be noted, however, that the 40 mesh stainless steel wire still gives a significantly improved discharge pattern as compared to a couch with no covering, or for that matter a IO I4 mesh, and may still be desirable because of the tendency of a finer mesh to fill up with white water fines (fibers). Also, the differences in the discharge pattern between the tested wires may be due at least in part to the difference in surface tension effects between stainless steel and bronze wires.

The above-discussed test results were gotten when the roll was rotated at a speed (peripheral velocity) of the general order of 1350-1380 feet per minute and a water rate of the order of lO30 plus gallons per minute.

In continuing research on the pilot model (No. 1 machine) attention was given to two areas: l) determining the best type of wire covering, and (2) evaluating the vacuum requirements for the fourth, final vacuum zone.

The basic approach to the testing was to have a number of different wires put on the couch and to take 0perational data on each covering. This data is summarized in Table I below and graphically plotted in FIG. 9.

10X 14 Mesh I40 Bad discharge at all conditions Bronze tried.

22x24 Mesh 528 Bad discharge at 20 GPM.

Bronze Good discharge at 30 GPM.

40 32 Mesh I280 Bad discharge at 20 GPM.

Bronze Good discharge at 25 8L 30 GPM,

50x36 Mesh 1800 Good discharge at 5, l0, l5 GPM Bronze & above. Lower rates cannot be controlled precisely, but it is estimated that conditions become unstable at 2-3 GPM.

55 36 Mesh I980 Good discharge at 2O & 3O GPM.

Bronze Shutting water supply off and (Fourdrinier turning on resulted in never type wire) losing the narrow jet except when there was no water flow to the felt.

*Calculuted from wire mesh.

Table 1 summarizes data on single bronze wire coverings. Based on the earlier tests, it was initially anticipated that a quite open wire would be unsuitableifor obtaining the desired discharge pattern while at some point a more closely woven (greater mesh number) wire would provide the desired discharge pattern. It is also believed that the mesh should be kept as open as charge pattern is dependent also upon both the fourth zone vacuum and the discharge rate.

Based on the operating data taken and the number of holes per square inch in the wire covering (calculated by multiplying the mesh numbers) tabulated in Table 1, FIG. 9 was prepared from the data of Table 1. FIG. 9 graphically indicates the approximate dividing line between a good and bad discharge pattern based on the discharge rate (assumed to be the same as the rate at which the felt was wet) and the total number of holes per square inch of the wire covering. Based on Table 1 and FIG. 9, a 50 36 mesh bronze wire should allow a good discharge pattern for just about any amount of water removed by the couch.

Additional data of interest on two other couch coverings were also taken. A double wire (bronze) covering was found to give acceptable results, but probably not as good as other single wire coverings. The testing of one 35x32 mesh stainless steel covering indicated that in some respects less desirable results are obtained with stainless steel wires than with bronze wires.

As previously mentioned, obtaining the best discharge pattern is also based on having a sufficient vacuum in the final zone for a given level of water removal (discharge) rate in addition to the proper wire mesh. Data taken on a 50x36 mesh bronze wire with varying vacuum levels in the fourth, final zone is summarized in Table 2 below. It should also be noted that once a good discharge pattern is obtained the equilibrium water carried in the wire in the fourth vacuum zone may be carried near the outer surface of the wire, making the wire surface glisten and wet to the touch; or it may be pulled into the wire with greater vacuum levels making the wire surface appear dull and dry to the touch. The data of Table 2 is shown graphicially in FIG.

Table 2 Minimum 4th Zone Vacuum to Obtain Good Discharge with Dry Wire Surface Minimum 4th Zone Vacuum to Obtain Good Discharge NutezAll data was taken using a 50x36 mesh bronze wire covering,

Based on the above-described, preparatory tests done on the converted Multi-Former roll as a pilot operation, a 50 36 mesh bronze wire was placed on a Manchester couch modified internally in accordance with the present invention and installed in a full paper machine of the Verti-forma type. The full paper machine was run on different types of paper involving different amounts of water handling, and the operation of the modified Manchester couch was highly satisfactory, further confirming the efficacy of the present invention.

However, it should be appreciated that in the application of the present invention there is no well defined single critical or magical range of workable mesh sizes of the preferred screen embodiment. The key factor is that the covering on the roll is a surface tension member, that is one which has a film-forming action with the water to produce a film-like collection of water at the transfer zone and at the final or void zone, all in combination with the overall water control zone as described above.

Although applicants experimental test work has shown that the effective mesh size has to be smaller than a 10X 14 mesh in order to work as a surface tension member" in combination with the rolls described, there is certainly a substantial range in mesh sizes possible. As stated above, there are many variables which affect the mesh size in the combination of the present invention and in the working environment in which the present invention operates. The primary and secondary technical factors known to the applicants which affect the precise mesh size are outlined below:

PRIMARY FACTORS SECONDARY FACTORS Type of material used in wire (for example bronze or stainless steel);

The particular, relative pressures in the water control zone including the vacuum available in the fourth zone 96 or vacuum requirements of the fourth zone 96;

to plug up with fiber fines weave of wire.

and other miscellaneous material in the water making the effective mesh size smaller.

As to plugging, it is noted that, as the wire mesh increases in number, the openings become smaller and there is a greater tendency for the wire to plug. White water (the water removed from the wet paper web) contains some quantity of fibers, fiber fines and other dissolved or particulate matter (additives) put into the stock for various reasons. (Particulate matter would include titanium dioxide, calcium carbonate and other fillers. Dissolved materials would include rosin, size, alum, wet strength resins, etc.). The easiest way to reduce the plugging tendency is to open up the wire using a lower mesh screen which has larger openings. How open the wire can be made will depend upon the vacuum available to the couch and the volume of water that can be handled, as well as the other factors tabulated above and discussed in greater detail herein. How closed the wire can be will depend upon the nature of the stock and the additives used. Generally long fibered stock such as some kraft bag paper will have fiber fines in the white water larger than a short fibered stock such as newsprint. The longer fiber stock would then be expected to require a more open wire.

Additionally the following factors affect the wire mesh size as purchased, that is the mesh size purchased may not indeed be the true mesh size in operation:

1. the manufacturing tolerances of the wire weaving equipment;

2. the operators skill in the manufacturing of the wire; and

3. the frictional drag between the papermaking wire and the suction roll wire.

Thus there is no single absolute for mesh size and too much emphasis should not be placed on the mesh size alone but rather on the operational characteristics and structural and method aspects of the combination taught in the instant specification, no single element or step alone being the absolute key to the present invention.

OTHER VARIATIONS While the preferred embodiments have been given by illustration only, there are obviously many ways in which the arrangement of a suction roll and in particular the couch could be designed incorporating the new and novel disclosure contained herein. For example, the high vacuum water collection zone could be broken into two or more sub-zones with their basic purpose being to remove water from the wet web. The lower vacuum zone might also be altered by an enlarged seal 112 having a wider face so that it could be a sealed zone functioning on residual vacuum carried in the couch roll holes from the high vacuum zone, with its purpose being to prevent the early release of the water below the collector pan. It is also within the spirit and scope of the invention that the release zone could be broken into two or more sub-zones which could be further modified with air pressure, atmospheric seals and- /or vacuum to alter the appearance and possibly the actual mechanism of the water discharge pattern; however the basic function of the release zone is to provide a vehicle to release a large quantity of water quickly in a concise pattern so that the water does not subsequently rim the couch roll and be thrown onto the incoming paper web.

It is also within the spirit and scope of the invention that various materials and designs could be conceived for possible surface tension coverings on the couch roll, although the most likely couch roll covering would be the metallic and plastic wires which are usually obtainable and are easily installed on the couch roll. The primary function of the couch roll coverings as has been beforementioned is to act as a surface tension member, while allowing the water extracted from the traveling web to be readily removed into and out of the couch roll openings at the appropirate time so that it can be removed from the web and then subsequently be thrown from the couch roll shell and the surface tension member into the collector pan without running around the couch roll or rimming the couch roll onto the incoming paper web.

From the foregoing, it can be seen that there has been provided a new and unique improvement in the papermaking industry which is capable of extracting large quantities of water from the traveling web as it passes over the couch roll or other type of suction roll and which accomplishes all of the objects and advantages hereinabove outlined. From a reading of the foregoing specification and a study of the attached drawings, it should become apparent that many changes in the details of construction and arrangement of the steps of the method may be made without departing from the spirit and scope of the invention as expressed in the accompanying claims and the invention is not to be limited to the exact manner shown and described, as the preferred embodiments have been given by way of illustration only.

What is claimed as invention is:

1. ln a papermaking process of the type wherein water is removed from paper that is being run over a suction roll, such as for example a couch roll, the improvement comprising the following steps:

a. providing the suction roll with a water control zone comprising a water collection section, a transfer section and a release section;

b. providing on at least a portion of the suction roll a surface tension covering around the periphery thereof;

c. applying a vacuum in the water collection section;

and

d. applying a relatively small vacuum 'n the transfer section in comparison to the magnitude of the vacuum being utilized in the water collection section, said surface tension covering and the vacuum differential coacting to cause the water to be held at the surface of the suction roll just prior to the release section so that it can be released in a controlled pattern.

2. The improvement as defined in claim 1 wherein in step (d) the vacuum in the transfer section is applied in a range from approximately 0 inches of water to approximately lO inches of water and the vacuum in the water collection section is applied in a range from approximately 5 inches of mercury to approximately 12 inches of mercury.

3. The improvement as defined in claim 1 wherein in step (d) there'is further included the step of providing in the release section a pressure that is approximately atmospheric pressure.

4. The improvement as defined in claim 1 wherein in step (b) said surface tension covering is provided by fixedly attaching at least one wire mesh screen to the outer surface of the suction roll.

5. The improvement as defined in claim 1 wherein in step (b) said surface tension covering is provided by fixedly attaching at least two wire mesh screens to the outer surface of the suction roll.

6. The improvement as defined in claim 1 wherein in step (b) said surface tension coveringis provided by utilizing lands and grooves machined on an existing suction roll..

7. The improvement as defined in claim 1 wherein in step (b) said surface tension covering is provided by fixedly attaching at least one non-metallic mesh screen to the outer surface of the suction roll.

8. The improvement as defined in claim 1 wherein in step (b) said surface tension covering is provided by fixedly attaching a plurality of wires over the existing openings in the suction roll.

9. The improvement as defined in claim 1 whereinin step (b) said surface tension covering is provided by fixedly attaching at least one metallic wire mesh screen to the outer surface of the suction roll, and'in step (d) the vacuum in the transfer section is applied in a range from approximately 0 to approximately 10 inches of water while the vacuum in the water collection section is applied in a range from approximately 5 to approximately 12 inches of mercury.

10. The improvement as defined in claim 9 wherein in step ((1) there is further included the step of providing in the release section a pressure that is approximately atmospheric pressure.

11. The improvement as defined in claim 1 wherein in step (b) said surface tension covering is provided by fixedly attaching at least one mesh screen having a mesh size higher'than 10 l4 mesh to the outer surface of the suction roll.

12. The improvement as defined in claim 1 wherein in step (a) there is further included the step of providing the water control zone with a fourth, final section, between the release section and the water collection section, the four sections spanning the full 360 of the roll, and in step (d) there is further included the step of providing in the final section a vacuum.

13. In a multi-zone suction roll, such as for example a couch roll, for a papermaking process of the type having a plurality of radial openings formed in the exterior shell of the roll and having a collector pan for collecting water that is thrown from the roll, the improvement which comprises:

a. transfer zone means for forming a transfer zone within the suction roll at a pre-determined location initiating at the point approximately where the paper stock leaves the roll and terminating approximately at the collector pan;

b. a surface tension covering formed on the surface of the suction roll, said surface tension covering allowing a film-forming action to take place between it and the water from the paper stock; and

c. vacuum means for creating a minimal controlled vacuum within the transfer zone sufficient to retain the water on the surface tension covering in a filmlike collection of water and in the suction roll openings against the centrifugal force tending to pull the water off the roll so that whenever the minimal vacuum is subsequently released the retained water will be thrown off the suction roll in a controlled directional pattern into the collector pan.

14. The improvement as defined in claim 13 wherein said surface tension covering comprises at least one wire mesh screen fixedly attached to the outer surface of the roll.

15. The improvement as defined in claim 14 wherein said screen has a mesh size higher than l 14.

16. The improvement as defined in claim 13 wherein said vacuum means creates a vacuum within the transfer zone in a range from approximately 0 inches of water to approximately 12 inches of water.

17. The improvement as defined in claim 13 wherein the improvement further comprises:

d. final zone means for forming a final vacuum zone within the suction roll at a pre-determined location initiating at the point approximately at the end of the collector pan and terminating approximately where the paper stock contacts the roll; and

e. second vacuum means for creating a controlled vacuum within the final zone sufficient to retain any residual water on the surface tension covering in a film-like collection of water and in the suction roll openings against the centrifugal force tending to pull the residual water off the roll or cause the residual water to rim along the roll so that the residual water will not be thrown onto the incoming paper stock.

18. In a suction roll such as for example a couch roll for a papermaking process wherein the suction roll has a plurality of radial openings formed in the exterior of the roll and wherein water collecting means is provided in proximity to the roll for collecting water that is extracted from the suction roll, the improvement comprising:

a. a surface tension member formed on the exterior surface of the suction roll, said surface tension member allowing a film-forming action to take place between it and the water from the paper stock;

b. water control zone means for providing a water control zone within the suction roll to control the water removed from the paper stock to the surface tension member to form a film-like collection of water and subsequently extracted from the suction roll to be deposited in the collecting means; and

c. pressure varying means for varying the pressure within said water control zone to directionally control the flow of water off the suction roll in a predetermined patter for deposit in the water collecting means.

19. The improvement as defined in claim 18 wherein said means for providing the water control Zone comprises means forming at least two zone sections, the pressure in one zone section being a variable vacuum sufficient to counteract the centrifugal effects of the rotation of the suction roll while the pressure in the other zone section is variable to release the water thereby allowing the centrifugal action of the suction roll on the water to pull the water from the surface tension member and into the water collecting means in a controlled pattern,

20. The improvement as defined in claim 18 wherein said water control zone means comprises means forming at least three zone sections wherein the pressure in the first zone section is variable between a large vacuum range and the pressure in the second zone section is variable between a smaller vacuum range as compared to the first zone section, and the pressure in the third zone section is variable in a range sufficient to allow the centrifugal force caused by the rotation of the suction roll to pull the water from the surface tension member and into the water collecting means.

21. The improvement as defined in claim 20 where said water control zone means further includes means forming a fourth zone section following said means forming said third zone section and having a vacuum range variable to prevent discharge of residual water from the suction roll openings.

22. A method for improving the removal of water in a paper-making process wherein a traveling paper web is subjected to various pressures induced from within a rotating suction roll such as for example a couch roll in order to remove the water from the roll to a collector pan positioned in proximity to the suction roll, comprising the steps of:

a. providing the exterior surface of the suction roll with a surface tension cover and providing the suction roll with a water control zone;

passing the web over the water control zone in the suction roll while inducing a predetermined vacuum of a relatively low, less-than-atmospheric pressure level in the water control zone;

c. raising the pressure level in the water control zone to a higher pressure level but still less than atmospheric pressure and sufficient to hold the water in the surface tension member against the centrifugal effect caused by the rotation of the suction roll; and

d. further raising the pressure level in the water control zone to a higher level sufficient to allow the water held in the surface tension member to be released in a controllable pattern by the centrifugal force caused by the rotational effect of the suction roll thereby allowing the water to be collected in the collector pan; steps b, c and d being performed sequentially with respect to the circumference of the suction roll.

23. The method as defined in claim 22 wherein in step (a) said surface tension cover is provided by forming a wire mesh screen around the exterior surface of the suction roll.

24. The method as defined in claim 23 wherein in inducing the vacuum in step (b) the vacuum is induced in a range from approximately 5 to approximately 14 inches of mercury.

25. The method as defined in claim 24 wherein in raising the pressure level in step (c) the pressure is raised to a range from approximately 0 to approximately 12 inches of water.

26. The method as defined in claim 25 wherein, in further raising the pressure level in step (d), the pressure is raised to approximately atmospheric pressure.

27. The method as defined in claim 22 further comprising the step of:

e. decreasing the pressure level in the water control zone to a pressure sufficient to retain any residual water, not released in step (d), in the suction roll.

28. In a suction roll such as for example a couch roll of the type used in the papermaking process and having a plurality of radial openings formed in the exterior of the suction roll and also having vacuum means within the couch roll for control of water removed from the paper in the papermaking process to the suction roll openings, the improvement comprising a surface tension member covering at least a portion of the suction roll, said surface tension covering allowing a filmforming action to take place between it and the water from the paper stock, said surface tension member serving as a means to aid in the removal of water from the paper stock by forming a film-like collection of water and in the subsequent discharge of the removed water into an exterior collecting means, said surface tension member also serving to retain any undischarged residual water in the couch roll openings by forming a film-like collection of water until it can be subsequently discharged by manipulation of the vacuum means.

29. The improvement as defined in claim 28 wherein said surface tension covering comprises a mesh screen.

30. The improvement as defined in claim 28 wherein said mesh screen has a mesh size higher than 14 mesh.

31. A water control and removal system for a multizone couch roll for a papermaking process, the couch roll being of the type having a plurality of radial openings formed in the exterior shell of the roll and having a collector pan for collecting water that is thrown from the roll, comprising:

a surface tension covering at the surface of the couch roll at least covering the radial openings in the ex terior of the shell of the roll, said surface tension covering allowing a film-forming action to take place between it and the water from the wet paper web;

transfer zone means for forming a transfer zone within the couch roll at a pre-determined location initiating at the point approximately where the paper web leaves the roll and terminating approximately at the collector pan;

transfer zone vacuum means for creating a minimal controlled vacuum within the transfer zone for holding the water on the surface tension covering in a film-like collection of water and in the couch roll openings at or near the surface of the couch roll shell against the centrifugal force tending to pull the water off the roll so that whenever the min imal vacuum is subsequently released the retained water will be thrown off the couch roll in a controlled directional pattern into the collector pan;

final zone means for forming a final vacuum zone within the couch roll at a pre-determined location initiating at the point approximately at the end of the collector pan and terminating approximately where the paper web contacts the roll; and

final zone vacuum means for creating a controlled vacuum within the final zone for holding any residual water on the surface tension covering in a filmlike collection of water and in the couch roll openings against the centrifugal force tending to pull the residual water off the roll or cause the residual water to rim along the roll so that the residual water will not be thrown onto the incoming paper web.

32. The system of claim 31 wherein there is further included:

water collection zone means for forming a water collection zone within the couch roll at a predetermined location initiating at the termination of said final zone means and terminating at the initiation of said transfer zone means;

water collection zone vacuum means for creating a controlled vacuum within the water collection zone at a pressure level lower than that in either the transfer zone or the final zone for drawing water from the wet paper web;

release zone means for forming a water release or discharge zone within the couch roll at a predetermined location initiating at the termination of said transfer zone means and terminating at the initiation of said final zone means; whereby there are four at least substantially contiguous zones spanning the full 360 degrees of the couch roll; and release zone pressure means for creating a pressure within the release zone at a level higher than that in the water collection zone, the transfer zone or the final zone for discharging the water theretofore held at or near the surface of the couch roll shell in a controlled directional pattern into the collector pan.

33. The system of claim 32 wherein the vacuum in the transfer zone is created in a range from approximately 0 inches of water to approximately 10 inches of water, and the vacuum in the water collection zone is created in a range from approximately 5 inches of mercury to approximately 12 inches of mercury.

34. The system of claim 32 wherein the pressure in the release zone is approximately atmospheric pressure.

35. The system of claim 32 wherein said surface tension covering comprises a mesh screen.

36. The system of claim 35 wherein said screen has a mesh size greater than a 10 l4 mesh.

37. The system of claim 35 wherein said screen has a mesh size of the range of approximately 30 to 60 mesh.

38. The system of claim 32 wherein the vacuum level in the final zone is in the range of approximately 2 inches to 4 inches of water.

UNITED STATES PATENT OFFICE CERTIFICATE OF CQRRECTION patent 3,902,960 Dated September 2, 1975 Thomas G Zentner et al Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2 lines 67 and 68 place quote marks before and after "Pulp and Paper Magazine".

. Column 3, line 1, Column 5, line 64, Column 13, line 9 and Column 15, line 43, place quote marks before and after "Verti-Forma", each occurrence.

. Column 14, lines 25 and 26, heading to the table,

Couch Wire Holes Covering Inch* Comments" should read Couch Wire Holes/Inch* Comments Covering Column 17 line 24 "removed" should read moved Signed and Scaled this 0 Nineteenth Day Of October 1976 [SEAL] Arresr:

RUTH c. MASON c. MARSHALL DANN Arresting Officer Commissioner rrfPalenls and Trademarks 

1. IN A PAPERMAKING PROCESS OF THE TYPE WHEREIN WATER IS REMOVED FROM PAPER THAT IS BEING RUN OVER A SUCTION ROLL, SUCH AS FOR EXAMPLE A COUCH ROLL, THE IMPROVEMENT COMPRISING THE FOLLOWING STEPS: A. PROVIDING THE SUCTION ROLL WITH WATER CONTROL ZONE COMPRISING A WATER COLLECTING SECTION, A TRANSFER SECTION AND A RELEASE SECTION: B. PROVIDING AT LEAST A PORTION OF THE SUCTION ROLL A SUFACE TENSION COVERING AROUND THE PHERIPHERY THEREOF: C. APPLYING A VACUUM IN THE WATER COLLECTION SECTON: AND D. APPLYING A RELATIVELY SMALL VACUUM IN THE TRANSFER SECTION IN COMPARISON TO THE MAGNITUDE OF THE VACUUM BEING
 2. The improvement as defined in claim 1 wherein in step (d) the vacuum in the transfer section is applied in a range from approximately 0 inches of water to approximately 10 inches of water and the vacuum in the water collection section is applied in a range from approximately 5 inches of mercury to approximately 12 inches of mercury.
 3. The improvement as defined in claim 1 wherein in step (d) there is further included the step of providing in the release section a pressure that is approximately atmospheric pressure.
 4. The improvement as defined in claim 1 wherein in step (b) said surface tension covering is provided by fixedly attaching at least one wire mesh screen to the outer surface of the suction roll.
 5. The improvement as defined in claim 1 wherein in step (b) said surface tension covering is provided by fixedly attaching at least two wire mesh screens to the outer surface of the suction roll.
 6. The improvement as defined in claim 1 wherein in step (b) said surface tension covering is provided by utilizing lands and grooves machined on an existing suction roll.
 7. The improvement as defined in claim 1 wherein in step (b) said surface tension covering is provided by fixedly attaching at least one non-metallic mesh screen to the outer surface of the suction roll.
 8. The improvement as defined in claim 1 wherein in step (b) said surface tension covering is provided by fixedly attaching a plurality of wires over the existing openings in the suction roll.
 9. The improvement as defined in claim 1 wherein in step (b) said surface tension covering is provided by fixedly attaching at least one metallic wire mesh screen to the outer surface of the suction roll, and in step (d) the vacuum in the transfer section is applied in a range from approximately 0 to approximately 10 inches of water while the vacuum in the water collection section is applied in a range from approximately 5 to approximately 12 inches of mercury.
 10. The improvement as defined in claim 9 wherein in step (d) there is further included the step of providing in the release section a pressure that is approximately atmospheric pressure.
 11. The improvement as defined in claim 1 wherein in step (b) said surface tension covering is provided by fixedly attaching at least one mesh screen having a mesh size higher than 10 X 14 mesh to the outer surface of the suction roll.
 12. The improvement as defined in claim 1 wherein in step (a) there is further included the step of providing the water control zone with a fourth, final section, between the release section and the water collection section, the four sections spanning the full 360* of the roll, and in step (d) there is further included the step of providing in the final section a vacuum.
 13. In a multi-zone suction roll, such as for example a couch roll, for a papermaking process of the type having a plurality of radial openings formed in the exterior shell of the roll and having a collector pan for collecting water that is thrown from the roll, the improvement which comprises: a. transfer zone means for forming a transfer zone within the suction roll at a pre-determined location initiating at the point approximately where the paper stock leaves the roll and terminating approximately at the collector pan; b. a surface tension covering formed on the surface of the suction roll, said surface tension covering allowing a film-forming action to take pLace between it and the water from the paper stock; and c. vacuum means for creating a minimal controlled vacuum within the transfer zone sufficient to retain the water on the surface tension covering in a film-like collection of water and in the suction roll openings against the centrifugal force tending to pull the water off the roll so that whenever the minimal vacuum is subsequently released the retained water will be thrown off the suction roll in a controlled directional pattern into the collector pan.
 14. The improvement as defined in claim 13 wherein said surface tension covering comprises at least one wire mesh screen fixedly attached to the outer surface of the roll.
 15. The improvement as defined in claim 14 wherein said screen has a mesh size higher than 10 X
 14. 16. The improvement as defined in claim 13 wherein said vacuum means creates a vacuum within the transfer zone in a range from approximately 0 inches of water to approximately 12 inches of water.
 17. The improvement as defined in claim 13 wherein the improvement further comprises: d. final zone means for forming a final vacuum zone within the suction roll at a pre-determined location initiating at the point approximately at the end of the collector pan and terminating approximately where the paper stock contacts the roll; and e. second vacuum means for creating a controlled vacuum within the final zone sufficient to retain any residual water on the surface tension covering in a film-like collection of water and in the suction roll openings against the centrifugal force tending to pull the residual water off the roll or cause the residual water to rim along the roll so that the residual water will not be thrown onto the incoming paper stock.
 18. In a suction roll such as for example a couch roll for a papermaking process wherein the suction roll has a plurality of radial openings formed in the exterior of the roll and wherein water collecting means is provided in proximity to the roll for collecting water that is extracted from the suction roll, the improvement comprising: a. a surface tension member formed on the exterior surface of the suction roll, said surface tension member allowing a film-forming action to take place between it and the water from the paper stock; b. water control zone means for providing a water control zone within the suction roll to control the water removed from the paper stock to the surface tension member to form a film-like collection of water and subsequently extracted from the suction roll to be deposited in the collecting means; and c. pressure varying means for varying the pressure within said water control zone to directionally control the flow of water off the suction roll in a pre-determined patter for deposit in the water collecting means.
 19. The improvement as defined in claim 18 wherein said means for providing the water control zone comprises means forming at least two zone sections, the pressure in one zone section being a variable vacuum sufficient to counteract the centrifugal effects of the rotation of the suction roll while the pressure in the other zone section is variable to release the water thereby allowing the centrifugal action of the suction roll on the water to pull the water from the surface tension member and into the water collecting means in a controlled pattern.
 20. The improvement as defined in claim 18 wherein said water control zone means comprises means forming at least three zone sections wherein the pressure in the first zone section is variable between a large vacuum range and the pressure in the second zone section is variable between a smaller vacuum range as compared to the first zone section, and the pressure in the third zone section is variable in a range sufficient to allow the centrifugal force caused by the rotation of the suction roll to pull the water from the surface tension member and into the water collecting means.
 21. The improvement as defined in claim 20 where said water control zone means further includes means forming a fourth zone section following said means forming said third zone section and having a vacuum range variable to prevent discharge of residual water from the suction roll openings.
 22. A method for improving the removal of water in a paper-making process wherein a traveling paper web is subjected to various pressures induced from within a rotating suction roll such as for example a couch roll in order to remove the water from the roll to a collector pan positioned in proximity to the suction roll, comprising the steps of: a. providing the exterior surface of the suction roll with a surface tension cover and providing the suction roll with a water control zone; b. passing the web over the water control zone in the suction roll while inducing a predetermined vacuum of a relatively low, less-than-atmospheric pressure level in the water control zone; c. raising the pressure level in the water control zone to a higher pressure level but still less than atmospheric pressure and sufficient to hold the water in the surface tension member against the centrifugal effect caused by the rotation of the suction roll; and d. further raising the pressure level in the water control zone to a higher level sufficient to allow the water held in the surface tension member to be released in a controllable pattern by the centrifugal force caused by the rotational effect of the suction roll thereby allowing the water to be collected in the collector pan; steps b, c and d being performed sequentially with respect to the circumference of the suction roll.
 23. The method as defined in claim 22 wherein in step (a) said surface tension cover is provided by forming a wire mesh screen around the exterior surface of the suction roll.
 24. The method as defined in claim 23 wherein in inducing the vacuum in step (b) the vacuum is induced in a range from approximately 5 to approximately 14 inches of mercury.
 25. The method as defined in claim 24 wherein in raising the pressure level in step (c) the pressure is raised to a range from approximately 0 to approximately 12 inches of water.
 26. The method as defined in claim 25 wherein, in further raising the pressure level in step (d), the pressure is raised to approximately atmospheric pressure.
 27. The method as defined in claim 22 further comprising the step of: e. decreasing the pressure level in the water control zone to a pressure sufficient to retain any residual water, not released in step (d), in the suction roll.
 28. In a suction roll such as for example a couch roll of the type used in the papermaking process and having a plurality of radial openings formed in the exterior of the suction roll and also having vacuum means within the couch roll for control of water removed from the paper in the papermaking process to the suction roll openings, the improvement comprising a surface tension member covering at least a portion of the suction roll, said surface tension covering allowing a film-forming action to take place between it and the water from the paper stock, said surface tension member serving as a means to aid in the removal of water from the paper stock by forming a film-like collection of water and in the subsequent discharge of the removed water into an exterior collecting means, said surface tension member also serving to retain any undischarged residual water in the couch roll openings by forming a film-like collection of water until it can be subsequently discharged by manipulation of the vacuum means.
 29. The improvement as defined in claim 28 wherein said surface tension covering comprises a mesh screen.
 30. The improvement as defined in claim 28 wherein said mesh screen has a mesh size higher than 10 X 14 mesh.
 31. A water control and removal system for a multizone couch roll for a papermaking process, the couch roll being of the type having a plurality of radial openings formed in the exterior sheLl of the roll and having a collector pan for collecting water that is thrown from the roll, comprising: a surface tension covering at the surface of the couch roll at least covering the radial openings in the exterior of the shell of the roll, said surface tension covering allowing a film-forming action to take place between it and the water from the wet paper web; transfer zone means for forming a transfer zone within the couch roll at a pre-determined location initiating at the point approximately where the paper web leaves the roll and terminating approximately at the collector pan; transfer zone vacuum means for creating a minimal controlled vacuum within the transfer zone for holding the water on the surface tension covering in a film-like collection of water and in the couch roll openings at or near the surface of the couch roll shell against the centrifugal force tending to pull the water off the roll so that whenever the minimal vacuum is subsequently released the retained water will be thrown off the couch roll in a controlled directional pattern into the collector pan; final zone means for forming a final vacuum zone within the couch roll at a pre-determined location initiating at the point approximately at the end of the collector pan and terminating approximately where the paper web contacts the roll; and final zone vacuum means for creating a controlled vacuum within the final zone for holding any residual water on the surface tension covering in a film-like collection of water and in the couch roll openings against the centrifugal force tending to pull the residual water off the roll or cause the residual water to rim along the roll so that the residual water will not be thrown onto the incoming paper web.
 32. The system of claim 31 wherein there is further included: water collection zone means for forming a water collection zone within the couch roll at a pre-determined location initiating at the termination of said final zone means and terminating at the initiation of said transfer zone means; water collection zone vacuum means for creating a controlled vacuum within the water collection zone at a pressure level lower than that in either the transfer zone or the final zone for drawing water from the wet paper web; release zone means for forming a water release or discharge zone within the couch roll at a pre-determined location initiating at the termination of said transfer zone means and terminating at the initiation of said final zone means; whereby there are four at least substantially contiguous zones spanning the full 360 degrees of the couch roll; and release zone pressure means for creating a pressure within the release zone at a level higher than that in the water collection zone, the transfer zone or the final zone for discharging the water theretofore held at or near the surface of the couch roll shell in a controlled directional pattern into the collector pan.
 33. The system of claim 32 wherein the vacuum in the transfer zone is created in a range from approximately 0 inches of water to approximately 10 inches of water, and the vacuum in the water collection zone is created in a range from approximately 5 inches of mercury to approximately 12 inches of mercury.
 34. The system of claim 32 wherein the pressure in the release zone is approximately atmospheric pressure.
 35. The system of claim 32 wherein said surface tension covering comprises a mesh screen.
 36. The system of claim 35 wherein said screen has a mesh size greater than a 10 X 14 mesh.
 37. The system of claim 35 wherein said screen has a mesh size of the range of approximately 30 to 60 mesh.
 38. The system of claim 32 wherein the vacuum level in the final zone is in the range of approximately 2 inches to 4 inches of water. 